This invention relates to safety seatbelt systems, and more particularly to a retractor system having electrical means for automatically unlocking a seatbelt retractor to allow the belt to be freely extended by the occupant before and during normal vehicle operating conditions upon occupancy of the seat at which the seatbelt is employed, but which automatically locks the retractor to prevent belt extension in response to certain abnormal vehicle conditions.
Emergency locking vehicle seatbelt systems of the prior art allow an occupant of the belt to perform normal body motions within the vehicle in a relatively unrestrained manner because the seatbelt can be freely extended and retracted to accommodate his motions. A retractor locking mechanism, or some other means operable to prevent belt extension, is provided for automatically preventing belt extension in response to an abnormal vehicular condition, such as a sudden acceleration, or deceleration, or an abnormal vehicle orientation. These conditions are normally associated with an accident in which it is desirable to restrain the vehicle's occupant against a sudden change in position within the passenger compartment of the vehicle.
Usually prior art automatic locking mechanisms employ some form of mechanical device for automatically locking or unlocking the retractor in response to a predetermined change in motion of either the vehicle or of the belt. A few automatic locking retractors of the prior art employ an electrical actuator such as a solenoid for locking or unlocking the retractor. The problem is that it is necessary for the locking mechanism to be locked in response to an abnormal condition. This abnormal condition could occur simultaneously with a failure of the vehicle's electrical system which would deenergize the solenoid.
A system utilizing a solenoid has been disclosed in U.S. Pat. No. 3,610,361. In that system, the retractor is normally unlocked to allow belt extension. The solenoid unlocks the retractor when the ignition circuit is energized to allow the user to adjust the length of the belt, so adjustment of the belt cannot be made until after ignition.